/*
** $Id: lapi.h $
** Auxiliary functions from Lua API
** See Copyright Notice in lua.h
*/

#ifndef lapi_h
#define lapi_h

#include "llimits.h"
#include "lstate.h"

/* Increments 'L->top', checking for stack overflows */
#define api_incr_top(L)                    \
    {                                      \
        L->top++;                          \
        api_check(L, L->top <= L->ci->top, \
                  "stack overflow");       \
    }

/*
** If a call returns too many multiple returns, the callee may not have
** stack space to accommodate all results. In this case, this macro
** increases its stack space ('L->ci->top').
*/
#define adjustresults(L, nres)                            \
    {                                                     \
        if ((nres) <= LUA_MULTRET && L->ci->top < L->top) \
            L->ci->top = L->top;                          \
    }

/* Ensure the stack has at least 'n' elements */
#define api_checknelems(L, n) api_check(L, (n) < (L->top - L->ci->func), \
                                        "not enough elements in the stack")

/*
** To reduce the overhead of returning from C functions, the presence of
** to-be-closed variables in these functions is coded in the CallInfo's
** field 'nresults', in a way that functions with no to-be-closed variables
** with zero, one, or "all" wanted results have no overhead. Functions
** with other number of wanted results, as well as functions with
** variables to be closed, have an extra check.
*/

#define hastocloseCfunc(n) ((n) < LUA_MULTRET)

/* Map [-1, inf) (range of 'nresults') into (-inf, -2] */
#define codeNresults(n)    (-(n)-3)
#define decodeNresults(n)  (-(n)-3)

#endif
